I have a 600KVA Delta-Wye transformer. It's secondary terminates in a separate cabinet at a circuit breaker. The wye neutral is not used in any of the power circuitry, and so it is connected to a ground bar at the transformer, along with the transformer's equipment bonding jumper. This ground bar is connected then to the building grounding electrode.
This circuit breaker, and various subsequent CB's and fuses, provide 480V power to a number of separate cabinets. Within this same cabinet, I have several 480V/120V single phase transformers. They also provide 120V power to a number of separate cabinets. In each cabinet there is a ground bar, to which is attached the cabinet equipment grounding conductor, transformer neutrals, and all other ancillary ground connections that are needed within the cabinet. These additional connections are for things like shielded wire, internally installed equipment cases, etc. We run each cabinet's equipment bonding jumper from this ground bar back to the transformer's ground bar.
The cabinets are typically connected together using metal conduit or raceway, but that isn't necessarily true in all installations.
We seem to get comments back from the field that our equipment bonding jumpers are improperly connected. Each comment tells us that they want something different done. (ok, maybe i'm exaggerating, but at times it seems that way). The two most popular responses seem to be to run the equipment bonding condutor back to 1) the building grounding electrode, or 2) the circuit breaker cabinet ground bar.
I submit this to the knowledgable people in this forum. The question I have is What is the proper way to bond the separate cabinets? At the Transformer? At the CB Cabinet? At the building grounding electrode?
This circuit breaker, and various subsequent CB's and fuses, provide 480V power to a number of separate cabinets. Within this same cabinet, I have several 480V/120V single phase transformers. They also provide 120V power to a number of separate cabinets. In each cabinet there is a ground bar, to which is attached the cabinet equipment grounding conductor, transformer neutrals, and all other ancillary ground connections that are needed within the cabinet. These additional connections are for things like shielded wire, internally installed equipment cases, etc. We run each cabinet's equipment bonding jumper from this ground bar back to the transformer's ground bar.
The cabinets are typically connected together using metal conduit or raceway, but that isn't necessarily true in all installations.
We seem to get comments back from the field that our equipment bonding jumpers are improperly connected. Each comment tells us that they want something different done. (ok, maybe i'm exaggerating, but at times it seems that way). The two most popular responses seem to be to run the equipment bonding condutor back to 1) the building grounding electrode, or 2) the circuit breaker cabinet ground bar.
I submit this to the knowledgable people in this forum. The question I have is What is the proper way to bond the separate cabinets? At the Transformer? At the CB Cabinet? At the building grounding electrode?